Block zeolite molecular sieve

Block zeolite molecular sieveZeolite molecular sieve is a type of aluminosilicate crystal with a regular microporous structure. It not only has the inherent physical and chemical properties of general inorganic membrane materials, but also has excellent properties. Its uniform and regular crystal pore system with specific spatial orientation and adjustable Si/Al ratio of the scaffold endow zeolite molecular sieve membrane with screening and shape selection functions, as well as adjustable surface properties, making it an excellent porous membrane material for achieving efficient separation and membrane catalytic reaction integration at the molecular level.

The mass transfer mechanism in zeolite molecular sieve membrane is mainly surface diffusion and activation diffusion. Surface diffusion includes adsorption and diffusion processes, where molecules first enter the pore surface of zeolite molecules from the separated phase, adsorb on the surface and in the pores, and the molecules adsorbed on the surface and in the pores transition from one adsorption point to a vacancy or another under the gradient of chemical potential, desorbing and diffusing into the permeable phase on the permeate side of the membrane. Activated diffusion is a process in which the adsorption between molecules and the surface of membrane materials is weak, and bulk molecules enter the pores and directly diffuse within them. Therefore, the selectivity of zeolite molecular sieve membrane separation varies due to differences in molecular adsorption and diffusion. The surface characteristics, pore structure, and molecular properties such as size and polarity of zeolite membrane materials determine the separation performance of the membrane. On the other hand, the effective separation layer supporting the zeolite membrane is composed of a polycrystalline zeolite layer. As it is a polycrystalline layer, the thickness, continuity, polycrystalline gaps, orientation, and other microstructures of the polycrystalline layer are the fundamental factors determining the separation effect of the zeolite membrane. Like other membrane materials, the key task of developing high-performance zeolite membranes is to design membrane materials and regulate the microstructure of the membrane based on the molecular characteristics of the separation system.

Block zeolite molecular sieveMolecular sieve adsorption is a physical phenomenon. The molecular sieve has a very high porosity and a large internal surface area, with internal voids accounting for about 50% of the volume. The determining factor of the adsorption performance of molecular sieve adsorbents is their own structure. In addition, different silicon aluminum ratios, equilibrium cations, pore and pore structures, as well as the formation and activation of molecular sieves, all affect the adsorption performance of molecular sieve adsorbents. Its adsorption effect mainly manifests in two aspects: selective adsorption based on the geometric size and shape of the molecule, and selective adsorption based on the polarity, unsaturation, and polarizability of the molecule.

There are various types of molecular sieves, which have high surface area and adsorption capacity, adsorption properties ranging from hydrophilicity to hydrophobicity, controllable acidity or other active centers, adjustable strength and concentration, regular pore size within the size range of most molecules, and cation exchangeability, providing many options for the development of adsorption separation technology. The adsorption process is a very complex process, and the performance of the adsorbent material plays a decisive role. The adsorption mechanism of molecular sieves is complex. The pore structure and pore environment of molecular sieves have a significant impact on their adsorption performance, and many adsorption processes are the result of the superposition of the two. Therefore, on the one hand, it is of great help to strengthen the research on the adsorption mechanism of molecular sieves and provide theoretical support for industrial applications and selection. On the other hand, strengthening customized research on the structure and composition of molecular sieves and developing low-cost and simple process synthesis technologies for new molecular sieve materials remains an important research direction.